Field of the Invention
The field of this invention relates generally to the field of hand-held power immersion blenders and more particularly toward those that are used to blend liquid food, such as sauces and soups. Immersion blenders are used in both commercial and home kitchens, and are suitable for blending other products in addition to food.
Description of the Prior Art
Prior art devices typically use an axial-flow cutter blade to blend the liquid. The leading edges of the blades are sharpened to cut the solid food mass that is suspended in the liquid. The blade is mounted to a shaft, and the shaft is rotatably mounted on bearings. The bearings are securely mounted inside a tubular support that extends to a motor housing. A shaft seal is placed on the shaft between the blade and lower bearing to protect the bearings from the liquid. A bell-shaped housing is attached to the blade end of the tubular support. The bell-shaped housing protects the blade and redirects the flow of liquid. The blade draws the liquid from the bottom of a liquid-holding container and discharges the liquid inside the bell-shaped housing that redirects the liquid towards the sides of the container.
The devices of the prior art have several drawbacks. One drawback relates to the shaft seal which is submerged in the liquid when the blender is being operated. During the operation of the blender, the liquid within the bell-shaped housing will be pressurized by the blade and the pressurized liquid is forced against the shaft seal. The dynamic action of the rotating shaft combined with the abrasive nature of the liquid food causes the seal to wear out. After the shaft seal fails, the liquid food by-passes the seal and ingress into the tubular support. The liquid food that remains inside the tubular support decomposes and results in bacterial growth. During the blending of subsequent batches of liquid food, the fresh batch of liquid food will then be forced inside the tubular support, which can become contaminated with the bacteria that previously formed inside the tubular support. When the blender is turned off, the liquid food that entered the tubular support will drain out of the tubular support into the fresh batch of liquid food thereby contaminating the fresh food with bacteria. This cross-contamination can cause offensive tastes and, more seriously, raise the potential for food poisoning. Further, the liquid ingression into the tubular support will cause the bearings to fail.
Another drawback with the prior art is with regard to operator fatigue that often occurs when using the larger commercial immersion blenders. Since blending within the body of liquid occurs mostly below the bell-shaped housing, the operator of the blender must move the blender around in the liquid to effectively blend the entire batch. If the blender is rested on the floor of the container, the liquid intake into the blade would become obstructed by the floor of the container and result in a reduction of blending efficiency. The spinning blade also creates a vortex in the liquid that bends upwards toward the surface of the liquid. The kinetic energy in the vortex will buffet the blender which can make the blender difficult to handle. Therefore, when using a larger commercial immersion blender the operator of the blender can become fatigued.